I've been a freelancer/consultant for a decade now. I was telling my Writing for the Media students about what I've learned and figured it was good enough for a blog post.

1) Never apologize for a perceived or actual lack of experience in an industry or niche. Spin any inexperience into a positive. For example, if you're bidding to write a healthcare website, say that your lack of corporate healthcare experience is helpful because your questions will be the same as your client's customer's questions.

2) Underpromise and overdeliver. Think you're going to have something done by Saturday? Tell 'em you'll have it to them by Monday. Then send it to them before Monday. Shows you're on the ball. Plus, if you get waylaid by life (it happens), no harm done, you won't have missed your deadline.

3) Always listen to client criticism and thank them for it in your response. The client is who you need to please. If they think enough of your work to criticize your path, then reevaluate. Your work will be better for it, and your client deserves some thanks for that.

Those are my top three. Who else has one?